1. Field of the Invention
The present invention relates to systems for writing data to nonvolatile memory and rewriting data already stored in a nonvolatile memory wherein electrically writing or rewriting data is possible.
2. Description of Related Art
Conventionally, as has been disclosed, for example, in Japanese Patent Application Laid-Open No. Hei 2-99746, an electronic device provided with a nonvolatile memory such as an EEPROM or flash EEPROM (hereinafter termed xe2x80x9cflash ROMxe2x80x9d) or the like to which data is electrically writable and capable of having a control program and control data stored therein has been proposed as a storage medium for storing a control program and control data for controlling a predetermined controlled object. According to such an electronic device, a control program and control data can be rewritten even after deployment in the market.
That is to say, the above-mentioned electronic device performs write processing so that when an external device separately provided is connected and a predetermined command is received from this external device, firstly, a write-control program sent from the external device is received and stored in a predetermined storage region of RAM, and subsequently by executing this write-control program in RAM, write data sent thereafter from the external device (i.e., the control program and control data for controlling the predetermined controlled object) is received, and this write data is written to nonvolatile memory.
The storage region of RAM to which the write-control program is to be stored, the storage region of nonvolatile memory to which the write data is to be written, the communication protocol of the communication conducted with the memory-writing device, and so on may vary from one electronic device to another.
In this regard, to enable data writing to nonvolatile memory to be performed even for electronic devices of such differing specifications, conventionally write-control information such as address information indicating a storage destination of the write-control program, address information indicating a write destination of the write data, and moreover the communication protocol, was sent from the memory-writing device to the electronic device, and a write-control program based on this write-control information was executed on the electronic-device side.
Accordingly, with a memory-writing device according to the related art, a personal computer or the like is connected and write-control information sent to the electronic device is modified each time that an electronic device of differing specifications is connected.
However, with the above-described memory-writing device according to the related art, each time that an electronic device of differing specifications is connected, a personal computer must be connected, and work is troublesome. Additionally, because the write-control information must be manually modified by operating a keyboard of the personal computer, it is possible to enter an erroneous value, and the desired data might not reliably be written to the nonvolatile memory of the electronic device.
In light of the above problems of the prior art, it is an object of this invention to provide a memory-writing device for an electronic device which can simply and reliably write desired data to a nonvolatile memory thereof.
It is a further object of this invention to provide an electronic control unit which can reliably prevent a control program and control data already stored in nonvolatile memory from being rewritten by an incompatible control program or control data, and a memory-rewriting system of a favorable memory-rewriting device and the electronic control unit for rewriting this control program and control data stored in nonvolatile memory of this electronic control unit.
It is a still further object of this invention to provide an electronic device which can rapidly rewrite data within its nonvolatile memory.
The above objects are achieved according to a first aspect of the present invention by providing a memory-writing device which can simply and reliably write desired data to a nonvolatile memory of an electronic device. Connection is made with an ECU to perform write processing to write data from the memory-writing device to a flash ROM by copying a write-control program from the external portion to a RAM and executing the write-control program, and by sequentially sending the foregoing write-control program and write data to this ECU together with sending, at a predetermined timing, write-control information required for the ECU to execute the write-control program. The write-control program and the write-control information are stored in a freely attachable and removable first ROM. The write-control information stored in the first ROM is read and sent to the ECU at a memory-rewriting device to cause the write processing to be performed in the ECU. According to this device, an ECU of differing specifications can be supported merely by exchanging the first ROM.
Other objects and features of the present invention will appear in the course of the description thereof, which follows.